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Procedure: Tekenreeksverzamelingen (LINQ) combineren en vergelijken (Visual Basic)

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In dit voorbeeld ziet u hoe u bestanden met regels tekst samenvoegt en vervolgens de resultaten sorteert. In het bijzonder ziet u hoe u een eenvoudige samenvoeging, een samenvoeging en een snijpunt kunt uitvoeren op de twee sets tekstregels.

Het project en de tekstbestanden instellen

  1. Kopieer deze namen naar een tekstbestand met de naam names1.txt en sla deze op in de projectmap:

    Bankov, Peter
Holm, Michael
Garcia, Hugo
Potra, Cristina
Noriega, Fabricio
Aw, Kam Foo
Beebe, Ann
Toyoshima, Tim
Guy, Wey Yuan
Garcia, Debra

  2. Kopieer deze namen naar een tekstbestand met de naam names2.txt en sla deze op in de projectmap. Houd er rekening mee dat de twee bestanden enkele namen gemeen hebben.

    Liu, Jinghao
Bankov, Peter
Holm, Michael
Garcia, Hugo
Beebe, Ann
Gilchrist, Beth
Myrcha, Jacek
Giakoumakis, Leo
McLin, Nkenge
El Yassir, Mehdi

Opmerking

Class ConcatenateStrings
    Shared Sub Main()

        ' Create the IEnumerable data sources.
        Dim fileA As String() = System.IO.File.ReadAllLines("../../../names1.txt")
        Dim fileB As String() = System.IO.File.ReadAllLines("../../../names2.txt")

        ' Simple concatenation and sort.
        Dim concatQuery = fileA.Concat(fileB).OrderBy(Function(name) name)

        ' Pass the query variable to another function for execution
        OutputQueryResults(concatQuery, "Simple concatenation and sort. Duplicates are preserved:")

        ' New query. Concatenate files and remove duplicates
        Dim uniqueNamesQuery = fileA.Union(fileB).OrderBy(Function(name) name)
        OutputQueryResults(uniqueNamesQuery, "Union removes duplicate names:")

        ' New query. Find the names that occur in both files.
        Dim commonNamesQuery = fileA.Intersect(fileB)
        OutputQueryResults(commonNamesQuery, "Merge based on intersect: ")

        ' New query in three steps for better readability
        ' First filter each list separately

        Dim nameToSearch As String = "Garcia"
        Dim mergeQueryA As IEnumerable(Of String) = From name In fileA
                          Let n = name.Split(New Char() {","})
                          Where n(0) = nameToSearch
                          Select name

        Dim mergeQueryB = From name In fileB
                          Let n = name.Split(New Char() {","})
                          Where n(0) = nameToSearch
                          Select name

        ' Create a new query to concatenate and sort results. Duplicates are removed in Union.
        ' Note that none of the queries actually executed until the call to OutputQueryResults.
        Dim mergeSortQuery = mergeQueryA.Union(mergeQueryB).OrderBy(Function(str) str)

        ' Now execute mergeSortQuery
        OutputQueryResults(mergeSortQuery, "Concat based on partial name match """ & nameToSearch & """ from each list:")

        ' Keep console window open in debug mode.
        Console.WriteLine("Press any key to exit.")
        Console.ReadKey()

    End Sub

    Shared Sub OutputQueryResults(ByVal query As IEnumerable(Of String), ByVal message As String)

        Console.WriteLine(System.Environment.NewLine & message)
        For Each item As String In query
            Console.WriteLine(item)
        Next
        Console.WriteLine(query.Count & " total names in list")

    End Sub
End Class
' Output:

' Simple concatenation and sort. Duplicates are preserved:
' Aw, Kam Foo
' Bankov, Peter
' Bankov, Peter
' Beebe, Ann
' Beebe, Ann
' El Yassir, Mehdi
' Garcia, Debra
' Garcia, Hugo
' Garcia, Hugo
' Giakoumakis, Leo
' Gilchrist, Beth
' Guy, Wey Yuan
' Holm, Michael
' Holm, Michael
' Liu, Jinghao
' McLin, Nkenge
' Myrcha, Jacek
' Noriega, Fabricio
' Potra, Cristina
' Toyoshima, Tim
' 20 total names in list

' Union removes duplicate names:
' Aw, Kam Foo
' Bankov, Peter
' Beebe, Ann
' El Yassir, Mehdi
' Garcia, Debra
' Garcia, Hugo
' Giakoumakis, Leo
' Gilchrist, Beth
' Guy, Wey Yuan
' Holm, Michael
' Liu, Jinghao
' McLin, Nkenge
' Myrcha, Jacek
' Noriega, Fabricio
' Potra, Cristina
' Toyoshima, Tim
' 16 total names in list

' Merge based on intersect:
' Bankov, Peter
' Holm, Michael
' Garcia, Hugo
' Beebe, Ann
' 4 total names in list

' Concat based on partial name match "Garcia" from each list:
' Garcia, Debra
' Garcia, Hugo
' 2 total names in list

De code compileren

Maak een Visual Basic-consoletoepassingsproject. Voeg een Imports instructie toe voor de System.Linq-naamruimte.

Zie ook